An electroluminescent (EL) display, such as an active matrix organic light emitting diode (AMOLED) display, may include an array of pixels. Each of the pixels may include an EL device, a switching transistor for transfer data that contains information on luminescence, and a driving transistor for driving the EL device to emit light according to the data. While such EL display enjoys the benefit of relatively low power consumption, display non-uniformity may exist among pixels due to process factors in semiconductor manufacturing. It may thus be desirable to have a circuit that solves the problem.